With the development of network technologies, new types of network structures emerge, such as the System Architecture Evolved (SAE). During the promotion of the SAE, the scenario in which an area is covered by both the SAE network and an existing network, such as a 2G or 3G network, occurs. As shown in FIG. 1, routing area (RA) 1 and RA 2 are covered by an existing 2G/3G network. A user equipment (UE) in the 2G/3G network needs to initiate a routing area update (RAU) request every time to change the RA. Tracking area (TA) 1 and TA 2 are tracking areas of the SAE network, similar to RAs in the 2G/3G network. TA 1 has intersected coverage with RA 1. In this case, when a multi-mode UE moves between these areas, the UE may frequently initiate network registration requests. For example, when the UE enters into RA 1, the UE registers with a serving GPRS support node (SGSN) of the 2G/3G network. When the UE enters into TA 1, the UE registers with a mobility management entity (MME) of the SAE network. When the UE moves from TA 1 to RA 1, the UE needs to register with the SGSN of the 2G/3G network again. Thus, significant air interface resources are wasted.
The bearer deletion method in the existing technologies applies to a single network. For example, after a UE performs the attach procedure in a 2G/3G network, if the SGSN is changed, the original attached SGSN receives the Cancel Location request from a home location register (HLR) and sends a Delete PDP Context Request message to a gateway GPRS support node (GGSN) to request for deleting the PDP context information when the UE exits upon exception last time. If no SGSN change occurs, the SGSN sends a Delete PDP Context Request message to the GGSN to request for deleting the PDP context information when the UE exits upon exception last time. That is, when the UE initiates an attach request or enters into a certain radio access technology (RAT) network by using the radio access technology for the first time and initiates an update location request, the accessed SGSN or MME needs to initiate a request to the serving gateway (S-GW) and PDN gateway (P-GW) to delete the original bearer if any. If no original bearer exists, the SGSN or MME initiates an update location request to the HSS. The HSS sends a cancel location request to the original SGSN or MME. If the original SGSN or MME has an original bearer, the SGSN or MME needs to initiate a request to the serving gateway (S-GW) and PDN gateway (P-GW) to delete the original bearer.